Metal deforming – With indication of condition or position of work – product,... – Including deformation by simple bending
Reexamination Certificate
2000-03-27
2001-07-31
Jones, David (Department: 3725)
Metal deforming
With indication of condition or position of work, product,...
Including deformation by simple bending
C072S389300, C072S702000
Reexamination Certificate
active
06266984
ABSTRACT:
TECHNICAL FIELD
This invention has for object a press-bending machine having improved features in the respetive press-bending with measuring and control system operating on at least four points of the bending angle. The innovation finds particular even if not exclusive application in the controlled sheet deformation on press-bend working.
BACKGROUND ART
Bending presses are known. They find wide use in the metal and mechanical industry, and in particular in the bending of metal sheets, for example for obtaining some differently shaped longitudinal sections, sometimes with the possibility of being taken up and, each of them, subjected again to a bending-pressing cycle. As a rule, it is possible to notice that a bending cycle consists essentially of the vertical descent of a tool up to touching the underlying metal sheet resting on the bench, in the carrying out of the bend, and then, at the end, in going back (lifting) up to reaching a starting position.
For carrying out the previous phases, the machine is made up of two parts, respectively a dynamic upper one (movable upper part), and a static lower one, making up the underside of the machine placed on the perpendicular of the dynamic part.
Regarding the dynamic part, in the execution of a bending cycle, the movable bending tool (elongated punch), made up of a blade differently shaped, also of the interchangeable type, effects exclusively a vertical to and fro movement, ensured by at least one oleodynamic cylinder, which determines the descent of an upper cross-piece which supports longitudinally said elongated punch, said punch operating towards a lower cross-piece that supports an interchangeable elongated matrix, followed by the eventual stop and lifting in the starting position.
In existing solutions, some drawbacks are noticeable. These, in general, concern the inaccuracy of the bending angle and in any way relate to an objective difficulty of predetermination and measuring of the bending angle. The traditional system provides that, giving a known total height of the matrix and depth of the groove in the matrix bending area, and the thickness of the sheet, the punch lowers to touch the sheet, then to further lower of a prestablished height to reach the required bending angle.
In the machines with numerical control, the punch descent is calculated mathematically on the base of some parameters set by the operator, and consequently, the machine is prearranged for executing the programmed angle. However the result is not always optimal, as such technique, many times leads to obtaining angles with some errors even if limited ones. This happens because of the presence of different factors, for example, the thickness of the sheets which is not constant, where even the incidence of few hundredths of a millimeter negatively influences the working.
For other reasons, because said predetermined theoretic calculation, such system does not offer the possibility of really checking the result, at the moment of bending, with the risk of endangering the productive process.
An additional factor having considerable character, relates to the natural elastic return of the material, which is calculated hypothetically and therefore in so far as it can be reliable, it may get close to the desired result, but it will never be considered as a real data.
Finally, besides the faultiness of the product, it is necessary to consider that the desired result is never attainable at the first bending cycle, that is at the first press-bending, but generally, a second press-bending phase is always necessary that intervenes to correct the first result.
With the aim of solving the problems pointed out, some complex press machines were conceived, which use a bending matrix supplied with an adjustable bottom, allowing to obtain a bending angle more precise than that of the traditional systems.
From a practical point of view, said matrix provides two surfaces coplanar and movable on horizontal plane defining in an intermediate position a longitudinal groove whose bottom may be eventually modified in height.
Such groove determines the momentary bending angle by means of the relative position of both the support surfaces on the side of the groove, which delimit its opening, and the bottom of the same groove.
Also in this hypothesis, however, persists a certain inaccuracy, one of whose causes is ascribable to the phenomenon of the elastic return of the sheet, a condition which occurs at the moment which follows the piece discharge, altering the bending angle originally determined and theoretically calculated.
Consequently, is necessary to proceed at first with some working tests, and, before starting the definitive bending production cycle, to carry out the due corrections on the numerical control, intervening on the pushing action of the punch and eventually on the position of the matrix bottom.
All this, besides requiring the intervention of specialised personnel, involves the machine stop and in conclusion, a considerable loss of useful time unavoidably influencing the relative production costs.
European Patent 340 167 (Hammerle) document, proposes a bending process according to a given nominal angle with the aid of a bending equipment made up of a punch and of a matrix, which is supplied with an adjustable bottom according to the angle to be formed.
The text points out that the process consists in that it provides:
in a first phase, the adjustment in height of the matrix bottom occurs on the basis of the first angle to be obtained, which is a little wider in respect to the given nominal angle, where the sheet is bent on the basis of this first angle by the lowering of the punch up to the matrix bottom;
in a second phase, the section is discharged, so that a return of the same in the stretched position occurs;
in a third phase the measured angle deriving from the returned and stretched section, is compared with the first angle and the position of the matrix bottom is adjusted with a value that corresponds to the nominal angle minus the difference between the angle measured on the released section and the first angle;
in a fourth phase the bent sheet is completely pressed by the punch again charged against the matrix bottom, which will take a correct position in height.
However even this solution is not free from drawbacks.
First of all, it appears as an extremely complex machine, not flexible and somewhat oversized, which needs a constant and accurate maintenance and setting-up, predominantly feasible by highly specialised personnel.
The consequence is, for the reference market, some high costs, above all related to the purchase and management of the machine itself. From a qualitative view-point, finally, said solution does not allow to obtain a sheet bending with the round corner on the extrados, therefore optimal for the next processing.
And in fact, it can be noticed that in the bending phase, by using a third dynamic point as mechanical element provided on the matrix bottom, the sheet in logic correspondence tends to be deformed, getting flat, practically becoming squashed, even if slightly, mainly in correspondence of the extrados of the bending angle.
A proposal, that can help to solve part of the problems previously pointed out, was put on the market by the Belgian Company LVD with the system named Easy-Form®.
Said system, consists in providing a movable arm, placed on the matrix side, which, supported by two articulations, and in bending phase, places a sensor means in contact with one of two wings of the diverging sheet.
Said sensor means, is coaxially movable in respect to said arm, and provides a measured data to the control logical unit of the machine. In this hypothesis, there are therefore three measuring points for giving parameters to the machine, two of which known, made up by the intersection corners of the plane with the matrix bending groove, and one variable and detectable by the oscillation with following positioning of said movable arm.
However, this is just because of the improper side position of the third point, dynamic, in respect to th
Conley, Rose & Taylon, P.C.
Jones David
LandOfFree
Metal sheet press-bending machine does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Metal sheet press-bending machine, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Metal sheet press-bending machine will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2554186